This invention relates to a method of conveying a solid material in pieces or parts, such as logs, chips or bark, with a conveyor using parallel, oblong transfer elements that move back and forth in the direction of transfer, most of the surface of the transfer elements, which are in contact with the material to be conveyed during the motion of transfer, moving in the direction of transfer at the same time and at least part of the surface of the transfer elements being inclined about its longitudinal axis, towards the centre of the conveyor. The invention relates also to a conveyor that is intended for conveying a solid material in pieces or parts, such as logs, chips or bark, and that is composed of parallel, oblong transfer elements that move back and forth in the direction of transfer, most of the surface of the transfer elements, which are in contact with the material to be conveyed, being movable in the direction of transfer at the same time and at least part of the surface of the transfer elements being inclined about its longitudinal axis, towards the centre of the conveyor.
In recent years, an apparatus according to patents FI 83181 and U.S. Pat. No. 5,063,981 has been developed for the transport of pulp wood, for example, which has proved to be very useful for feeding pulp wood into a barking drum. In the apparatus, the friction force between the pieces to be conveyed is increased by inclining the transfer elements with the result that the pieces do not tend to move backward during the return motion of the transfer elements. The apparatus according to said invention requires, however, a relatively large number of transfer elements. In practice, 6 to 8 transfer elements are needed whose movement has to be accurately controlled to make the apparatus operate in the correct way. Today, the pulp wood feeding devices according to the known invention are usually provided with beam-like, roller-supported transfer elements. This results in a relatively expensive structure comprising a great number of parts.
The conveyor according to the invention is characterised in that the pieces or parts lying on the inclined, outermost transfer elements are carried by means of the lower longitudinal edge of the outermost transfer elements, the angle of inclination of said edge about the longitudinal axis being smaller than the angle of inclination of the upper edge of the outermost transfer elements;
whereby the support force exerted by the outermost transfer elements on the pieces or parts lying thereon, and the friction force between the outermost transfer elements and the pieces or parts lying thereon, increase;
and whereby the support force exerted by second transfer elements situated lower with respect to the outermost transfer elements, on the pieces or parts lying thereon, and the friction between said second transfer elements and the pieces or parts lying thereon, decrease.
The conveyor according to the invention is characterised in that at least in some of the transfer elements, the angle of inclination of the lower part of the transfer elements about the longitudinal axis is smaller than the angle of inclination of the upper pan thereof.
According to the invention, the load exerted on the lateral transfer elements of the conveyor, which usually are inclined at an angle of at least 45xc2x0 towards the centre, is increased by transferring an extra load that results from a change of direction of the packing forces is caused by the loads of said elements to them. The surface of the outermost transfer elements of the conveyor can be bent in such a way that the inclination of the lower edge of the transfer elements is equal to or somewhat greater than the angle at which the following transfer element is inclined towards centre of the conveyor.